Flexible ducts are designed for a wide variety of uses, e.g., to transport fluids such as heated, cooled or exhaust air, or air mixed with other gasses or particulate matter, or both. Specifically, flexible ducts may be employed in residential or office buildings as components of heating, ventilating and air conditioning systems, or in industrial plants to carry away dust and fumes. In such applications, and in the process of being installed therein, flexible ducts are subjected to a variety of forces that may cause damages of such kind and extent as to render the ducts unsuitable for safe and effective use. Thus, it is essential to have flexible duct with sufficient strength to resist these forces. The present applicant has addressed this need, and has designed a flexible duct that exhibits exceptional strength.